Enclosed crawlspaces beneath buildings usually have soil floors and are contained by a concrete or masonry wall that extends down to the footings. Moisture is a concern in crawlspaces because it can create environmental conditions that are favorable for the growth of mildew, molds, and other kinds of fungi. One source of moisture in crawlspaces is the water vapor that escapes from the soil. Leaks or drainage that infiltrate the crawlspace are another common source of moisture. At certain humidity levels, the moisture in the crawlspace atmosphere will condense within the crawlspace. Standing condensate creates a nuisance and can foster the growth of unhealthy microorganisms such as Legionella bacteria. Condensed moisture also absorbs into porous surfaces and fosters rot that results in the deterioration of structural components such as wooden joists. Even when the moisture does not result in structural deterioration and health problems, it can lead to the creation of undesirable musty odors.
To reduce the humidity levels in crawlspaces to levels that discourage the condensation of moisture, it is desirable to ventilate the crawlspace. Ventilation, in addition to reducing moisture levels, serves to vent out other gases such as radon and vapors from termite treatment. To promote ventilation, it is common to provide ventilation openings in the wall or foundation surrounding the crawlspace. For example, many building codes specify that the walls surrounding crawlspaces must have ventilation openings of not less than 1 square foot for each 150 square feet of crawlspace area.
It is very common to cover ventilation openings with foundation vents that have a grid or bars at the exterior face to exclude debris and vermin such as mice and insects. Most foundation vents are installed in openings that measure 8 inches high by 16 inches wide, which is the space that would be occupied by a standard masonry block. Some foundation vents feature a shutter which can be closed to seal the vent during cold weather. Foundation vents with shutters come in manually-operated and automatic versions, the shutters in the automatic versions generally being opened and closed through the action of a bi-metal coil that operates without electricity. In addition, some foundation vents incorporate an electrically-powered fan to force air to vent from the crawlspace.
There are various ways of installing foundation vents depending on their design, A common way of installing vents is by applying a bed of cement, caulking, or other adhesive at the bottom of the opening in the foundation, setting the vent into the opening, and then securing the vent edges with a surface coat of the cement, caulking, or other adhesive. Another means of securing foundation vents is to drill holes into the foundation wall and then secure the vent with nails, screws, or wall anchors. Some foundation vents are secured to foundation openings by tabs that are either pressed against or nailed to the circumferential face of the opening. Such means of securing vents require the installer to spend time and use tools to install a vent. Vents which require the use of adhesives or the creation of holes in the foundation wall also can result in unsightly marring of the foundation. Thus, there is a need for a foundation vent that can be quickly installed without tools, adhesives, or the need to use fasteners such as screws and nails.